An apparatus for plucking fibers from fiber bales comprising pressed fiber materials and assembled in a row can have a cutting member traveling to and fro over the row of fiber bales and progressively lowered to mill fibers from the tops of the bales. These devices are also known as bale mills.
The apparatus can have a horizontally movable cutting device comprising a cutting member which can be raised or lowered and formed with at least one cutter roller, and an air passage through which the fibers which may have the form of tufts or the like plucked off by the cutting member can be sucked continuously from the vicinity of the cutter roller into a fixed collector passage which is connected to a vacuum source. The top of the collector passage is sealed by a cover strip, which is released only at the entrance mouth, i.e. the location at which the air passage from the cutting device opens into it.
It is known to attach each end of the cover strip, which is approximately twice as long as the collector passage, to an edge of the entrance mouth and to guide it from there around a first guide roller provided at one end of the collector passage, under the collector passage to a second guide roller provided at the other end, and from there to the other edge of the entrance mouth where it is attached. The cover strip slides, therefore, on the upper side of the collector passage with the back and forth motion of the cutter device, and is acted upon by friction developed on the upper side of the collector passage, so that it wears quickly and, therefore, must be replaced often.
In order to avoid the friction developed between the moving cover strip and the collector passage, it is known to use a cover strip which is more than three times as long as the collector passage and to attach it at one end of the collector passage; from that end this cover strip extends along the top of the collector passage to a guide roller provided adjacent one edge of the entrance mouth of the air passage by which it is guided upwards; then the cover strip extends back to said end of the collector passage above the point at which it is attached; then the cover strip passes around a guide roller mounted at the aforementioned end of the collector passage and under the collector passage, around a guide roller provided at the other end of the collector passage, to a guide roller provided at the outer edge of the entrance mouth of the air passage and from there runs along the top of the collector passage back to the other end of the collector passage where it is attached. Of course, then the surface of the cover strip does not move relative to the collector passage when the cutting device moves, and friction due to such motion is eliminated. However, a cover strip of an excessive length and four guide rollers for diverting the strip by 180 degrees are required.
In another arrangement one end of a cover strip is attached to one end of the collector passage, and its other end is wound and unwound about a roller provided adjacent the entrance mouth of the air passage of the cutting apparatus and driven by a motor. On the other side of the entrance mouth a slider for closing the other portion of the collector passage is provided. This arragement, of course, avoids excessive length for the cover strip, but requires an additional motor, which moreover develops considerable heat and may cause a variety of maintenance problems.